Prolonged survival after complete resection of disseminated melanoma and active immunotherapy with a therapeutic cancer vaccine.

PURPOSE: The curative effect of surgery in certain patients with metastatic melanoma suggests the presence of endogenous antitumor responses. Because melanoma is immunogenic, we investigated whether a therapeutic cancer vaccine called Canvaxin (CancerVax Corporation, Carlsbad, CA) could enhance antitumor immune responses and thereby prolong survival. PATIENTS AND METHODS: Of 263 patients who underwent complete resection of American Joint Committee on Cancer stage IV melanoma, 150 received postoperative adjuvant vaccine therapy and 113 did not. The overall survival (OS) for the two groups was compared by Cox regression. Further survival analysis was performed by matched-pair analysis according to three prognostic variables: sex, metastatic site, and number of tumor-involved organ sites.
RESULTS: Five-year OS rates were 39% for vaccine and 19% for nonvaccine patients. On multivariate analysis, vaccine therapy was the most significant prognostic variable in this cohort (P =.0001). Analysis of 107 matched pairs of vaccine and nonvaccine patients revealed a significant OS advantage for vaccine therapy (P =.0009): 5-year OS was 39% for vaccine patients versus 20% for nonvaccine patients. There was a significant delayed-type hypersensitivity (DTH) response to adjuvant vaccine therapy (P =.0001), and OS was significantly correlated with DTH to vaccine (P =.0001) but not with DTH to purified protein derivative (PPD), a control antigen.
CONCLUSION: Prolonged survival was observed in patients who received postoperative active immunotherapy with Canvaxin therapeutic cancer vaccine. The correlation of survival with vaccine-DTH responses but not PPD-DTH indicates a treatment-specific effect. These findings suggest that adjuvant active specific immunotherapy should be considered after cytoreductive surgery for advanced melanoma.